Analysis of the data on recurrence time distribution of the immunogenic fibrosarcoma will be completed. Experiments planned relating to the C parvum studies are: efficacy of C parvum given i.v. to cause permanent regression of fibrosarcoma transplanted at several sites (liver, brain, wall of urinary bladder, wall of colon, uterus, kidney, skin, muscle, subcutaneous tissue); assess role of C parvum dose - to use continuously infused (i.p.) and massive doses; determine efficacy of C parvum alone or admixed with tumor antigen given not only before irradiation but after tumor regression; examine for correlation between delayed hypersensitivity reactive against C parvum or tumor antigen and tumor regression; similar test using macrophage spreading inhibition; compare efficacy of C parvum and glucan. For the various tumors under study our intent is to enumerate macrophage in individual tumor and test for correlation between macrophage number and tumor response. Related to this is the examination for an understanding of the variation in response of members of an inbred strain of mice to tumor. Role of T lymphocyte and macrophage in determining regression pattern of tumor will be evaluated. Comparison of inactivation of fibrosarcoma cells in vivo and in vitro will be made. Attempts to understand the apparent greater sensitivity in vivo will include analysis of role of pH. BIBLIOGRAPHIC REFERENCES: Suit, H.D., Sedlacek, R., Wagner, M., Orsi, L., Silobrcic, V. and Rothman, K.: Effect of Corynebacterium parvum on the Response to Irradiation of a C3H Fibrosarcoma. Cancer Research 36:1305-1314, 1976. Suit, H.D., Sedlacek, R.S., Silobrcic, V. and Linggood, R.M.: Radiation Therapy and C parvum in the Treatment of Murine Tumors. Cancer 37:2573-2579, 1976.